Method and apparatus for tail threading of a paper web in a finishing machine for paper

ABSTRACT

A device in a finishing machine for paper is arranged to guide a paper web along a predetermined path. The traction device ( 2 ) engages a tail of the web or an auxiliary member ( 6 ) for transferring the tail of the web. The device has power transmission of its own by means of which is moves in relation to a guide ( 1 ) extending in the machine direction. The traction device moves in relation to the guide by friction contact of one or several drive wheels ( 3 ) with the guide ( 1 ). The friction contact plane of the guide ( 1 ) curves in directions perpendicular thereto in accordance with the travel path of the paper web.

The invention relates to a method for tail threading of a paper web in a finishing machine for paper that is arranged to guide a paper web along a predetermined path, wherein in the method the tail of the web or an auxiliary member for tail threading of the web are drawn by means of a traction device comprising power transmission means of its own that transmit the traction device in relation to a guide extending in the machine direction. The invention also relates to an apparatus for tail threading of a paper web in a finishing machine for paper, comprising a threading device that is arranged to guide the tail of the paper web along a predetermined path.

In the finishing machine of paper, which in this invention includes for example a coating machine, a calender, a slitter winder, a rereeler, a laminating machine and a printing machine, the threading of the paper web takes place at a speed lower than the actual running speed of the machine. Lower speed can be utilized when starting to feed the paper web again from a new reel through the finishing machine. When the paper web has been passed through the machine at a low threading speed, it is possible to accelerate the machine to the actual running speed (production speed). The tail of the paper web refers at this stage to such a paper web that is passed through the finishing machine before the machine is accelerated to the full running speed, irrespective of the production width of the web that may vary.

For example in a coating machine the web travels from an unwinder to a reel-up under the guidance of many rolls via coating stations and drying sections. In such machines the travel path of the web typically contains a large number of upward and downward directed sections and the path can be very winding. An example of such path geometry is for example the EP patent 611716 that discloses a machine comprising two coating stations to coat the paper web on both sides.

The threading devices are for example belts or ropes that guide for example a narrower lead-in strip separated from a full-width web through the machine. At a suitable stage the lead-in strip is spread into a full-width web by means of diagonal cutting. In complicated transfers the threading ropes or belts require several rope pulleys, belt guiding wheels or the like, as well as a return circulation for the belts or ropes. The threading ropes or belts require a traction device and a tightener to maintain suitable tension. The traction device, the tightener and the return section of the ropes/belts occupy a great deal of space in the basement. Furthermore, during threading the belts or ropes move within their entire length, which increases the possibility of malfunctions.

U.S. Pat. No. 4,883,209 suggests as a threading device for a treatment device of a paper web comprising complicated threading processes an elongated fillet travelling next to the web and comprising a hose in which pressurized medium is supplied. When the hose expands, it moves a carriage in front of itself, the tail of the web being attached to said carriage with a rope. A problem in such an apparatus is that it is not possible to determine the threading speed precisely. The apparatus requires a long actuator (hose) extending on the entire length, which constitutes a factor of uncertainty in the function of the threading apparatus, and it is difficult to perform long threadings of tens of metres by means of the apparatus.

The U.S. Pat. No. 3,761,001 discloses a carriage intended for threading that travels along a rail in a printing machine. The carriage is electrically operated and it may contain a battery. The rail comprises a toothed bar equipped with cogged wheels to guide the carriage and to accomplish a draw. The rail contains branching sections and crossing sections for transferring the carriage as well as the tail of the web via alternative routes through different printing sections. There may also be two carriages connected one after the other.

In the method according to the U.S. Pat. No. 3,761,001 the tail of the web is thus drawn by means of a traction device comprising a power transmission member of its own that transmits the traction device in the direction of a guide extending in the machine direction. In the US patent this is implemented in such a manner that power is transmitted by means of a power transmission mechanism from the battery to a cogged wheel that is in contact with a cogging extending in the longitudinal direction of the guide. Especially in FIGS. 7 to 9 of the patent it can be seen that to implement the alternative routes shown in FIG. 1, the guides curve in the direction of the plane of the cogging. This complicates the travel of the carriage in threadings in which the path contains steep, frequently occurring curves. It is a problem of the cogging that impurities originating from the process, for example paper strips or coating paste may accumulate between the teeth and hamper the function of the guide.

It is an aim of the invention to present a method that does not contain the above-identified problems. To implement this, the method is characterized by the features presented in the claims.

In the invention a traction device is moved along a guide with one or several drive wheels that produce a movement in relation to the guide by means of friction contact. The guide curves in a direction perpendicular to the plane of the friction contact in accordance with the winding of the path. The friction contact surface does not require coggings or other corresponding shapings, but it may be a straight surface. Advantageously, the friction contact surface of the guide is straight in the cross-section perpendicular to the longitudinal direction of the guide, ending on both ends with a rectangular edge.

According to a preferred embodiment, the pressing force of one or several drive wheels is attained by means of counter wheels affecting from the opposite side of the cutting contact plane.

According to yet another embodiment, the friction contact is attained by means of a belt or the like passed around at least one drive wheel and one or several other wheels.

According to a preferred embodiment used especially in coating machines, the transfer rate of the hold point of the finishing machine and the speed of the traction device are adjusted with respect to each other in such a manner that the end of the web drawn by means of the traction device travels substantially at the transfer rate of the hold point. When the finishing machine operates at the threading speed that is clearly lower than the normal running speed, it is possible to utilize the hold points in the threading. For example when the end of the web in the form of a narrow lead-in strip reaches the first such a hold point by which it is possible to exert a tractive force on the tail of the web, it is possible to start drawing the section of the tail of the web preceding the hold point by means of the hold point at the same time when the traction device continues the threading of the tail of the web from the hold point onward. In the threading section preceding the hold point it is thus possible to spread the web into a wider one, for example into full width.

It is also possible to first draw a special auxiliary rope on the entire threading path by means of the traction device and to attach the rope thereafter from the traction device to a separate, for example stationary traction device by means of which the tail of the web attached to the rope is drawn on the threading path.

The guide travelling in the machine direction may extend on the entire threading path on the tending side, complying with the travel path of the web. The reliability of the threading process can be ensured, because a constant force can be more accurately adjusted in the lead-in strip drawn by the traction device or in the auxiliary rope by means of which the entire web is drawn.

Another aim of the invention is to introduce a threading apparatus located in the finishing machine for paper web that is less complex than the threading ropes and belts of prior art. To attain this purpose, the threading device is primarily characterized in that the drive wheel is arranged in a friction contact with the friction contact plane of the guide, and the friction contact plane of the guide curves in directions perpendicular thereto in accordance with the travel path of the paper web.

The traction device is advantageously a carriage comprising power transmission means of its own for moving the carriage along the guide. The source of power of the carriage is advantageously electricity. The electric power source is advantageously a battery that travels along with the carriage. To adjust the threading speed accurately to other conditions, especially to the threading speed of the finishing machine, the speed of the carriage can be adjusted, advantageously in a stepless manner. The speed adjustment is preferably implemented by means remote control, wherein it is possible to change the speed during the movement of the carriage.

According to a preferred embodiment, the traction device contains several carriages connected one after the other and having separate functions. The carriages are connected in such a manner that they turn in the plane of curvature of the guide so that the device can comply with the curves of the guide, both with the outer and inner curves. The carriages have different functions so that one carriage functions as a driving carriage and the others comprise power sources (batteries), control electronics and transmitter/receiver functions.

The guide extending in the machine direction has a simple structure in that respect that the only part moving during the threading is the traction device, and long continuous functional parts (ropes, belts, hoses) are not necessary. Furthermore, a return circulation of the belt or rope is not required, but the guide comprises an initial end and a final end between which the traction device can travel back and forth from the initial end to the final end during threading, and during the return movement from the final end to the initial end to a new initial position of the threading. Alternatively, the carriage can be detached from the guide at the final end and carried separately to the leading end to wait for a new threading. It is also possible to arrange a return guide in the apparatus that does not follow the threading path, but is intended to return the threading device to the opposite direction in the starting point of threading. The cross-section of the guide for the parts guiding the traction device can be very simple, i.e. the friction contact plane can be straight in the plane perpendicular to the longitudinal direction of the guide, and on both edges on the other side of the same there may be contact planes parallel thereto for the counter wheels of the traction device.

The guide may be provided with straight sections and curved sections in accordance with the path geometry. Furthermore, it is possible to provide the guide, at least for a part of its length, with a flow of cooling medium at least for the sections that are located by the hot processing means of the finishing machine, for example by the calender rolls.

In the following, the invention will be described in more detail with reference to the appended drawings, in which

FIG. 1 shows a threading device according to the invention at different stages in a side-view at the location of the rolls of the finishing machine,

FIG. 2 shows a traction device and a guide in a cross-sectional view on a plane perpendicular to the longitudinal direction of the guide,

FIG. 3 shows a tractive carriage of the traction device and the guide in a perspective view,

FIG. 4 shows the entire traction device in a side view on the straight section of the guide,

FIG. 5 shows a side view of the traction device in a curve,

FIG. 6 shows a side-view of a coater in which the threading apparatus can be used,

FIG. 7 shows in perspective the function of the threading device at the separation point of the lead-in strip,

FIG. 8 shows in perspective the function of the threading device at the hold point of the coater,

FIG. 9 shows a traction device according to a second embodiment in a side-view in the inner curve,

FIG. 10 shows the traction device of FIG. 9 in the outer curve,

FIG. 11 illustrates the operating principle of the traction device a of FIGS. 9 and 10, and

FIG. 12 shows a traction device according to a third embodiment of the invention in a principle view.

In the following, the operating principle of the traction device will be described. FIG. 1 shows a threading apparatus travelling by a roll 5 in a finishing machine for paper, said apparatus comprising a guide 1 whose cross-section will be described in more detail hereinbelow, and a traction device 2 arranged movable in the guide and comprising supports or the like for keeping the traction device in contact with the guide and guiding it along the guide. The movement of the traction device along the guide 1 is attained by means of one or several drive wheels that are in a power transmitting connection with the guide 1 and obtain their driving force from power sources described hereinbelow. The drive wheel is arranged to rotate on bearings in the traction device, and it is in a power transmitting contact with the guide by means of friction. Power transmission means connect the drive wheel to a drive motor moving along with the traction device. The power transmission may be for example a reduction gear. The drive motor 4 is an electrical motor that receives its driving force from a battery arranged to move along with the traction device.

To the traction device 2 a lead-in strip is attached either directly or by means of an elongated auxiliary member 6 transmitting tensile stress, such as an auxiliary rope, to which the leading tail of the paper web can be attached. The traction device can be equipped both with a fastening point for the auxiliary rope and with fastening means of the narrower lead-in strip separated from the paper web to fasten the web directly to the traction device. The scope of the invention also covers the idea according to which the traction device 2 is only utilized for pulling the auxiliary member, which during the movement of the traction device is not in a tensile stress transmitting contact with the web, and it is not until the auxiliary member is pulled with a device independent from the traction device, for example with a stationary winder that the actual tail of the web is pulled on the threading path.

FIG. 1 shows a situation in which the traction device travels on the guide 1 on the side of the inner curve, i.e. on the roll 5 side of the guide. The future travel path of the paper web along which the paper web is arranged to travel by means of the threading device is marked with the letter W. The fastening between the traction device and the guide is arranged such that the traction device complies well with the winding of the guide, being sometimes in the inner curve, i.e. on the side of the centre of curvature, and sometimes in the inner curve, i.e. on the opposite side of the guide in relation to the centre of curvature. The drive wheels of the traction device 2 are in a constant power transmitting friction contact with the guide 1 in the straight and curved sections. The plane of the guide along which the drive wheels roll extends in an elongated shape with a predetermined width in the machine direction and its width direction coincides approximately with the cross-machine direction.

The guide 1 can be positioned on the entire length of the finishing machine, for example on the tending side to a location in which threading ropes or belts have been used previously. The guide extends on the side of the future travel path of the paper web, and a lead-in strip or an auxiliary means directed backwards therefrom extends diagonally towards the middle. The straight sections of the guide are located in points where the travel path of the web is nearly straight, and there may be curved sections by the different rolls and cylinders and air turning devices and by other devices that change the direction of the paper web.

In the following, the structure of the guide 1 and the traction device 2 will be described in more detail

FIG. 2 shows a cross-section of the guide 1 and the tractive carriage 21 of the traction device 2. The guide is preferably an elongated rail made of metal that has a predetermined profile shape (standard cross-section). The primarily guiding section of the guide is a flat bar 1 a extending in the machine direction and curving in both directions in a direction perpendicular to its plane in accordance with the windings of the path. When necessary, it is possible to strengthen the flat bar at suitable locations on the side opposite to the friction contact side of the carriage by means of a stiffening structure in suitable sections. The figure shows a stiffening profile 1 b extending in the longitudinal direction of the guide, said stiffening profile forming a closed pipe with the flat bar 1 a, whereby a channel 1 c is formed inside the pipe and cooling medium, such as water, can be supplied therein. The profile is dimensioned in such a manner that both edges of the flat bar 1 a remain free within a distance of predetermined length in the width direction. The guide is preferably prefabricated in such a manner that it can be assembled by fastening elements of predetermined length abuttingly together.

The tractive carriage 21 is connected to the guide against the flat bar 1 a by means of wheels positioned on the opposite sides of its plane. The tractive carriage comprises drive wheels 3 positioned above the flat bar, said wheels transferring the carriage while rotating by means of friction drive when they are in a sufficiently strong contact with the upper surface of the flat bar. On the lower side of the flat bar, close to both edges there are counter wheels 4 a, one before the contact point of the drive wheel and the other after the contact point, said counter wheels, when positioned in contact with the lower surface of the flat bar, lock the carriage 21 to the guide 1. The terms upper surface and upper side of the flat bar and the lower surface and lower side of the flat bar refer to the different sides of the plane of the flat bar, and the surface shown as an upper surface in the figure is not necessarily always positioned upward.

The fastening point of the threading of the web is located in the carriage 22 following the tractive carriage 21. As a result of this the tractive carriage is only subjected to forces parallel to the rail and centrifugal forces resulting from the curves of the guide 1 that affect perpendicularly to the plane of the flat bar 1 a.

The sideways locking of the tractive carriage 21 is attained by means of control wheels 4 b positioned against the edge of the flat bar from the sides, said control wheels being also arranged rotatable on bearings in the tractive carriage 21.

The tractive carriage 21 also comprises a drive motor M and power transmission means for transmitting the rotation of the drive motor with a suitable transmission ratio to the drive wheels 3. FIG. 3 shows the tractive carriage 21 in perspective. The drive motor M rotates a cogged wheel H1 located at the end of its shaft, said cogged wheel transmitting the torque to a larger cogged wheel H2 to whose shaft the drive wheels 3 are fastened. In the figure there are two drive wheels next to each other, and they are sufficiently wide to attain a good contact with the friction contact surface of the guide (the upper surface of the flat bar).

The drive motor M, the power transmission means (cogged wheels) and the drive shaft of the drive wheels 3 are fastened to the frame R1 of the carriage that is primarily composed of two vertical frame plates located on both edges. The counter wheels 4 a and the control wheels 4 b are arranged on bearings to rotate freely in a second frame R2 composed of the outer frame plates, said frame being arranged movable with respect to the first frame to set the pressing force of the drive wheels 3. In the figure the frames are articulated tumable with respect to each other.

As can be seen in the figure, there are two motors M, one in front of the wheels (3) and one behind them, and they both rotate a cogged wheel H1 of their own. The cogged wheels are in a torque transmitting contact with the same main cogged wheel H2 on different locations of its periphery.

Behind the tractive carriage 21 a fastening carriage 22 of threading is attached as the next carriage, to which fastening carriage it is possible to attach the end of a rope, belt or a corresponding element that is in contact with the web. This carriage contains freely rotating wheels 4 a, 4 b that are positioned against the flat bar 1 a from opposite sides on both edges of the flat bar, two of said wheels being positioned successively in pairs on both edges. The wheels 4 a, 4 b located on different sides of the flat bar are connected to each other by means of a swinging arm located outside the edge of the flat bar, said swinging arm being capable of turning in such a manner that when the carriage is pulled, the wheels are pressed against the flat bar 1 a on opposite sides. The fastening carriage 22 is subjected to a lateral force, i.e. a force affecting in the direction of the plane of the flat bar 1 a that results from the tail of the web or the auxiliary member of threading drawn behind. The fastening carriage comprises a force measurement sensor arranged in the fastening point, by means of which it is possible to constantly measure and monitor the force used for drawing the tail of the web. The force information can be transmitted to a control station wirelessly.

The force measurement sensor can also be arranged in the threading means, for example in the middle of the auxiliary tractive member producing tensile stress, such as a rope that is attached from one end to the fastening carriage and from the other to the web.

The fastening carriage is followed by a control electronics carriage 23, a communication carriage 24 (reception of control messages and transmission of measurement messages) and a battery carriage 25 that are coupled successively to each other. Between the carriages there are the necessary electrical couplings to control the speed of the tractive carriage, to transmit signals between the carriages and to supply driving force to the motor. As can be seen in FIG. 4, the carriages following the tractive carriage 21 comprise pairs of wheels 4 a, 4 b positioned against the flat bar on opposite sides of the flat bar (on different sides of the main plane of the flat bar). The wheels 4 a, 4 b located on different sides of the flat bar can be connected with a rocking arm that is articulated to the frame of the carriage. Some of the wheels, for example the wheels 4 b located on the upper surface of the flat bar can be equipped with flanges, wherein their larger diameter flanges ensure the lateral position of the carriage. The carriages can also be connected successively in such a manner that the shaft connecting some of the wheels transversely with respect to the travel direction at the same time forms the joint for the connection, wherein this pair of wheels is in a way shared by the carriages.

By dividing the device drawing the web in the threading into several carriages connected in the vertical plane in the machine direction (in the plane of the guide perpendicular to the friction contact plane of the flat bar) to turn in relation to each other, the traction device can travel in curves having small radius, as illustrated in FIG. 5, in which the traction device has bent in the inner curve as a result of the articulations between the carriages. The adjustment of the last carriages 24, 25 to the same small turning radius at the location of the curve is illustrated by means of the guide drawn with dotted lines.

FIGS. 4 and 5 illustrate primarily the chassis structures and wheels of the carriages. It is obvious that the carriages can be provided with different types of housings or covers to protect the parts therein.

In view of the operation it is important that the rotating speed of the drive wheels 3 can be adjusted and maintained constant as accurately as possible and that the attained movement speed of the carriage is directly and linearly proportional to this rotating speed, and the travel direction in relation to the gravity (the “ascents” and “descents” of the guide) has no affect thereon. The contact of the drive wheels 3 to the guide 1 must be such that the linear speed along the guide is dependent solely on the speed of rotation of the drive wheels. The movement speed is adjusted by adjusting the rotating speed of the drive motor by affecting its electric input variable. The adjustment takes place advantageously by means of remote control through the communication carriage 24 so that the travel speed of the traction device can be rapidly adjusted to the threading speed of the finishing machine, if necessary.

In the following the threading in an off-coating machine or off-calender will be described as an example. The traction device is positioned on the guide 1 in the unwinder. A longitudinal auxiliary member (hereinbelow auxiliary rope) or a lead-in strip is fastened to the second carriage 22 of the traction device 2. If an auxiliary rope is used, its other end is taped to the lead-in strip or to a full-width paper web whose tail is pretreated in a suitable manner, and the traction device pulls the lead-in strip or the full-width paper web by means of the auxiliary rope. The web or the lead-in strip is thus unwound from the paper reel located in the unwinder. If a lead-in strip is used, it is cut in a known manner from the full-width paper web by means of a cutting device, for example by means of a diagonal cutting device, by means of which the cutting point can be changed in the cross-machine direction, and the rest of the web is directed to a broke processing system, such as a pulper. The width of the lead-in strip is typically approximately 100 to 300 mm. By means of such a diagonal cutting device it is possible to spread a narrower lead-in strip into a full-width web as the threading proceeds. It is also possible to use a pre-cut lead-in strip that is unwound from a reel of its own and seamed at a suitable stage to the actual web drawn through the machine. The tail of the web (the lead-in strip or a full-width web) is drawn by the carriage and guided by the guide through a coating machine or calender at the normal threading speed (typically 30 to 100 m/min). The traction device travels to the reel-up drawing the tail of the web at the same time behind itself. When the traction device arrives to the reel-up, the auxiliary rope or lead-in strip is separated therefrom. The auxiliary rope of the reel-up or the lead-in strip can be attached to a winder that maintains the tension of the lead-in strip or the auxiliary rope. By means of the winder it is possible to wind the lead-in strip until the full-width web following thereafter enters into a position in which it can be transferred to the reeling core.

It is also possible that when the auxiliary rope is used, it is so long that the full-width web does not follow the threading movement of the traction device, but the traction device is first utilized to pass the auxiliary rope on the entire length of the machine, and when the traction device is in the end of the guide, the auxiliary rope and the web attached to its final end (possibly only at this stage) is drawn on the travel path of the web on the entire length of the machine by means of the winder. Such an auxiliary rope may be of pulpable quality. Its tensile strength can be arranged in such a manner that it is capable of drawing the web through the finishing machine, but breaks in sudden tensile stresses. Thus, risks in occupational safety are not caused if the rope ends up in the vicinity of the rolls and cylinders of the finishing machine that rotate at the running speed or are accelerated to the running speed.

When the full-width web following the lead-in strip or the auxiliary rope has been passed through the entire machine by running the machine at the threading speed, the web is lifted up on the reeling core of the reel-up and the entire machine is accelerated to the actual running speed.

The traction device can be transferred from the reel-up manually back to the initial position via the same guide via which the threading was conducted. Alternatively, the carriage can be released from the guide and transferred back in another way. There may be several carriages, wherein the initial end always contains one or several carriages ready.

According to one alternative, it is possible to equip the apparatus with a special return guide along which the traction device can travel back by means of its own operating force. The return guide can be positioned below the finishing machine, for example below the floor level.

FIG. 6 shows as an example a four-station coater that is intended for coating the paper web on both sides. The principle is that in such a machine the paper web is coated on both sides twice, and after each coating station there is a drying section in the travel direction of the web. The drying section contains successively a contactless dryer in which the drying of the recently coated web takes place on contactless principle, and a drying cylinder group in which the web is dried on contact principle. The figure illustrates how there may be several upward and downward directed threadings and a large number of winding sections in the machine, in which the path curves to opposite directions, for example especially at the location of the drying cylinder groups. In the coater shown in the figure, the first hold point P is in the location in which the web enters the space between the cylinder 7 of the first drying cylinder group R1 and the drying wire 8 after the coating station C1. The first drying cylinder group R1 is shown in a larger scale at the bottom of FIG. 6. In the travel direction of the web and in the direction of propagation of the threading this hold point P is preceded by a contactless dryer D1 through which the web is passed from above from the coating station C1 to the drying cylinder group R1. Other coating stations are marked with the references C2, C3 and C4, the contactless dryer following each station correspondingly with the references D2, D3 and D4, and the drying cylinder group following each contactless dryer correspondingly with references R2, R3 and R4. The unwinder at the initial end of the coating machine is marked with the reference numeral 9 and the reel-up at the final end with the reference numeral 11. Between the last drying cylinder group R4 and the reel-up there is also a calender 10. The guide 1 travels through the entire coater from the unwinder 9 to the reel-up 11 at least in such a manner that it travels via all coating stations and the drying sections following thereafter. The coating machine is not necessarily similar to the one described above. It may contain fewer than four coating stations, for example only two coating stations to coat the web on both sides.

In the coating machine the threading distance may be significantly longer when compared to the length of the machine measured on the floor level because of the complicated transfers in which the web can start moving to the incoming direction at several points. Thus, threading distances of over 100 meters measured along the path are common, and in the four-station coating machine of FIG. 3 the distance is over 200 meters. The drawing of the narrow lead-in strip only with the traction device for distances over 100 meters is not reasonable because of the breaking risk. When a traction device 2 travelling along a guide is used for drawing the tail of the web, the steps illustrated in FIG. 8 are taken, in other words, the tail of the web is transferred from the unwinder to the first hold point P described above solely with the force of the traction device 2, whereafter the transfer movement of the hold point produces a traction between the unwinder and the hold point. FIG. 8 shows how the guide 1 follows the winding travel of the web and is located outside the peripheral surfaces of the cylinders of the cylinder group R1 that are arranged rotatable on bearings, and curves in accordance with the peripheral surfaces that guide the web. The traction device 2 is located in the point in which it has drawn the lead-in strip 12 between the peripheral surface of the drying cylinder 7 and the drying wire 8. The traction device 2 travels at the speed of the coating machine, which in an off-coating machine is typically 30 to 100 m/min during the threading. Thus the lead-in strip 12 following thereafter travels at the speed of the peripheral surface of the cylinder 7 and the drying wire 8. The belt is attached to the traction device in the drawing direction by means of an elastic auxiliary member 6, for example a rubber band, so that small differences between the surfaces of the traction device 2 and the surfaces of the machine do not cause tension in the attachment between the traction device 2 and the lead-in strip 12. When the lead-in strip 12 remains between the drying wire 8 and the cylinder 7, the drawing of the lead-in strip shifts to the drying group. FIG. 8 shows a traction device 2 composed of one carriage, and the power transmission and the fastening point of the threading means are located in the same carriage. Such an alternative also belongs within the scope of the invention. In the situation of FIG. 8, it is possible to use a traction device 2 with several carriages as well. The fastening point of the elastic auxiliary member 6 can thus be located in the carriage following the traction device.

As can be seen in FIG. 7, there is a point before the hold point P in the travel direction of the lead-in strip 12, in which point the lead-in strip 12 is separated from the full-width web W by means of a cutting device 13, for example by means of a waterjet cutter, and the remaining part is conveyed down to the pulper 14 or to a corresponding broke processing system. The cutting device 13 is a diagonal cutter that is capable of moving in the cross-direction of the web (arrow S), and to spread the strip 12 into a full-width web when moving from the tending side to the operating side. The spreading takes place at a suitable stage, preferably after the lead-in strip 12 is already drawn by the hold point P. Thus, at least in the initial section of the machine it is possible to start conveying a web wider than the lead-in strip 12, although the traction device has not yet proceeded to the end of the threading path.

The traction device 2 travels through the entire drying cylinder group at the speed of the drying cylinders and the drying wire. After the drying cylinder group the initial end of the lead-in strip 12 is no longer guided by the drying cylinders and the drying wire. The traction device 2 draws the initial end of the lead-in strip 12 again to the next hold point in the free section following the drying cylinder group.

The invention is not restricted solely to be used in the above-identified coaters, but other off-machine processing machines, such as calenders are also possible, in which a guide can be used for guiding the tail of the web or the auxiliary member preceding the tail through the calender nips.

FIG. 9 shows a traction device according to a second embodiment in a side-view in the inner curve of the guide. The guide 1 is shown as a full circle with the intention of illustrating in how small a radius of curvature the traction device 2 is capable of moving. The first element in the traction device is the motor carriage 20, from which the power transmission to the tractive carriage 21 takes place by means of a belt transmission located at the side. The tractive carriage 21 also contains the necessary control electronics and the transmission and reception of messages, i.e. it also comprises the functions of the control electronics carriage and the communication carriage. This is followed by a series of carriages connected successively, of which carriages at least some carry the batteries necessary as power sources for the motor carriage 20, i.e. they correspond to the battery carriages 25 of the previous embodiment. It is possible that some carriages do not contain batteries, wherein they function only as intermediate carriages that connect two successive carriages to each other. The last carriage in the travel direction is the fastening carriage 22 of threading that may also contain batteries. The end of the member connected to the web can be attached to this carriage.

FIGS. 9 and 10 also show counter wheels 4 a that enter in contact with the guide from the opposite side, said counter wheels functioning on the same principle as hereinabove, in other words they ensure that the wheels of the carriages are pressed with a sufficient force against the friction contact plane of the guide 1. The counter wheels 4 a are arranged at the ends of arms articulated to turn in the plane of curvature of the guide. The pressing force can be set by means of a spring 4 c that is connected to the arm in a power transmitting contact. At least some of the wheels of the traction device contain side flanges that extend below the friction contact plane of the guide, i.e. they guide the traction device sideways in relation to the guide 1. FIGS. 9 and 10 also illustrate how successive carriages share freely rotating wheels 4 b in the articulation points between the carriages.

FIG. 11 shows in a simplified manner the operating principle of the traction device of FIGS. 9 and 10, when a traction device of only three carriages is used as an example. A belt 3 a is passed around the drive wheel 3 of the tractive carriage, the belt being actually in direct friction contact with the plane of the guide. On the inner surface of the belt there is advantageously a cogging that meshes with a corresponding cogging on the outer periphery of the drive wheel 3. The belt is also passed around other freely rotating wheels 4 b in such a manner that it forms a closed loop and is in contact with the wheels 4 b also above, at the location of the return section of the loop. Said belt 3 a travels via the freely rotating wheels 4 b of all the succeeding carriages. At the location of the last wheel 4 b of the last carriage 22 there is a tightening member 4 c (FIGS. 9 and 10), such as a spring by means of which it is possible to adjust the tension of the entire belt loop. Furthermore, the carriages comprise auxiliary wheels 15 by means of which it is possible to adjust the shape of the belt loop to the outer curves and inner curves in such a manner that the belt does not become excessively tightened or loosened. These auxiliary wheels 15 are positioned against the belt in the return section of the loop between the wheels 4 b under the loading of the springs 4 d (FIGS. 9 and 10).

By means of the belt 3 a it is possible to attain a contact for a longer distance in the longitudinal direction of the guide 1, and thus the tension remains even if there was oil or water on the surface of the guide.

FIG. 12 shows schematically a third embodiment of the invention. The carriages can be equipped with mere wheels or a belt loop passed around the wheel, similarly to the solutions hereinabove. It is a special feature herein that the tractive carriage 21 of the traction device 21 is located after the carriages 23, 25 containing the control electronics, the transmission and reception functions and the power sources (batteries) in the travel direction of the device, i.e. in the direction of propagation of the threading, and it draws the fastening carriage 22 of threading after itself. This illustrates the fact that the traction carriage does not necessarily have to be the first one of the several carriages of the traction device, but it can push carriages comprising other functions in front of it, the only prerequisite being that it transmits traction to the threading member that can be connected directly to the traction carriage or to a separate fastening carriage connected thereafter.

The structure of the guide 1 can be arranged in the appropriate manner, taking into account for example the conditions of the finishing machine. In the area of the coating stations and the calender, a guide is advantageously used, inside of which a flow of cooling medium, for example water, is arranged, and here it is possible to use a hollow profile formed on the other side of the flat bar. The need for cooling can occur for example in the vicinity of hot rolls of the calender, and in infra dryers and flotation dryers. In coating stations the cooling medium is advantageous in that respect that the outer surface of the guide can be arranged to condensate, whereby it can be kept clean.

When a power source, such as a battery moving with the traction device is utilized, it is possible to arrange a charger for charging the batteries at a suitable location in the guide. This charger can be located for example in the unwinder, and it can be placed in such a manner with respect to the guide 1 that the traction device can be charged without removing it from the guide.

As was mentioned above, the returning of the traction device to the initial end of threading in the threading apparatus can be a return guide. The guide 1 can thus form a closed loop comprising a threading section extending in the travel direction of the web, and a return section extending in the opposite direction preferably underneath, the final end of said return section possibly comprising a charging station for charging batteries. Furthermore, there may be several traction devices 2 in use, which wait for their turn in the unwinder.

The loading station can also be located in the reel-up before the beginning of the return section of the guide. Also in this case there may be several traction devices 2 waiting for their turn. Thus, a charging station is not necessary in the unwinder.

The guide 1 may also comprise branches, i.e. alternative travel paths that correspond to the alternative threading paths of the finishing machine. Each of these points can be equipped with a mechanical gear that guides the traction device to the correct path.

Furthermore, it is possible to arrange the transmission of operating power to the traction device 2 in other ways than by means of an accompanying power source (battery). It is for example possible to provide the guide with a power rail from which the carriage can receive its driving power and transmit it to the power transmission means with which the carriage moves along the guide. However, when the operating environment is taken into account, a guide with a simple structure and no power transmission is the most reliable and safe solution. 

1-31. (canceled)
 32. A method for tail threading of a paper web in a finishing machine for paper that is arranged to guide a paper web along a predetermined path, the method comprising the step of drawing a tail of the web or an auxiliary member for threading the tail of the web with a traction device comprising power transmission of its own by which the traction device moves in relation to a guide extending in the machine direction, wherein the movement of the traction device in relation to the guide is attained by a friction contact of one or several drive wheels of the traction device with the guide, and wherein the guide has a friction contact plane which curves in directions perpendicular thereto in accordance with the travel path of the paper web.
 33. The method of claim 32, wherein, in threading, one or several successively coupled carriages are used as the traction device, said carriages being articulated to turn with respect to each other in the plane of curvature of the guide, wherein said one or several drive wheels are located in a different carriage than the fastening point of the tail of the web or the auxiliary member for threading the tail of the web.
 34. The method of claim 33, wherein three or several successively coupled carriages are used, which are articulated to turn with respect to each other in the plane of curvature of the guide, and in which at least a power source is positioned in a carriage of its own.
 35. The method of claim 34 wherein the power source comprises a battery.
 36. The method of claim 32 wherein a pressing force of the one or several drive wheels is attained by counter wheels effective on an opposite side of the friction contact plane of the guide.
 37. The method of claim 32 wherein the friction contact is attained by means of a belt passed around at least one drive wheel.
 38. The method of claim 32 wherein in the tail threading of the web a lead-in strip that is narrower than the full-width web is first transferred at least to a section of predetermined length in the machine direction of the finishing machine, whereafter the lead-in strip is followed by a full-width web.
 39. The method of claim 32 wherein the predetermined path contains at least one hold point capable of transferring the tail of the web at a predetermined transfer rate irrespective of the traction device, and the transfer rate of the hold point of the finishing machine and the travel speed of the traction device along the guide are adjusted with respect to each other in such a manner that the tail of the web drawn with the traction device travels substantially at the transfer rate of the hold point.
 40. The method of claim 39 wherein the tail of the web comprises a lead-in strip which is directly connected to the traction device.
 41. The method of claim 32 wherein the tail of the web is transferred simultaneously with the movement of the traction device and drawn with the traction device via the auxiliary member that transmits tensile stress.
 42. The method of claim 39 wherein the tail of the web is drawn in the drawing direction with an elastic auxiliary member.
 43. The method of claim 32 wherein by means of the traction device the auxiliary member, which transmits tensile stress, is first drawn at least to a section of predetermined length in the machine direction of the finishing machine without a drawing contact to the tail of the web, and thereafter the tail of the web is drawn on the same section by means of the auxiliary member transmitting tensile stress.
 44. The method according of claim 32 wherein the guide is utilized to guide the traction device, and with said traction device the tail of the web and/or the auxiliary member, at least partly via a winding path that contains sections curved in opposite directions.
 45. The method of claim 32 wherein the guide is utilized to guide through at least one coating station the traction device, and with said traction device the tail of the web and/or the auxiliary member.
 46. The method of claim 32 wherein the guide is utilized to guide through at least one calendering nip the traction device and with said traction device the tail of the web and/or the auxiliary member.
 47. The method of claim 32 wherein the guide is utilized to guide from an unwinder through the entire finishing machine to a reel-up, the traction device and with said traction device the tail of the web and/or the auxiliary member.
 48. The method of claim 32 wherein the tail comprises a lead-in strip which is spread into a full-width web at the same time as it is drawn by the traction device.
 49. The method of claim 32 wherein the guide is cooled down by a cooling medium at least for a part of its length.
 50. The method of claim 32 wherein the speed of the traction device is adjusted during threading by remote control.
 51. The method of claim 32 further comprising the step of measuring the force affecting the fastening point of the tail of the web or the auxiliary member in the traction device during threading.
 52. An apparatus for tail threading of a paper web in a finishing machine for paper, in which the paper web is arranged to travel along a predetermined path, wherein the apparatus comprises a threading device comprising a guide extending in the machine direction, as well as a traction device for the tail of the web that is arranged to move along and in relation to the guide, said traction device comprising a drive wheel connected to the power transmission of the traction device itself, said drive wheel being arranged to transfer the traction device in relation to the guide by means of a power transmitting contact between the guide and the drive wheel, and wherein the drive wheel is arranged in a friction contact with a friction contact plane of the guide and the friction contact plane of the guide curves in directions perpendicular thereto in accordance with the travel path of the paper web.
 53. The apparatus of claim 52 wherein the guide comprises an elongated profile having an outer surface which the drive wheel contacts.
 54. The apparatus of claim 53 wherein the elongated profile comprises a flat bar.
 55. The apparatus according to claim 53, wherein the traction device comprises counter wheels positioned against the surface of the profile on an opposite side of the profile with respect to one or several drive wheels.
 56. The apparatus of claim 55 wherein one or several drive wheels and the counter wheels are connected to different frame parts attached together to move with respect to each other in a direction perpendicular to the friction contact plane of the guide.
 57. The apparatus of claim 52 wherein the traction device contains two or several successively coupled carriages that are articulated to turn with respect to each other on the plane of curvature of the guide, and in which the drive wheel or drive wheels and a fastening point of the tail of the web or the auxiliary member are located in different carriages.
 58. The apparatus of claim 52, wherein the traction device comprises three or several successively coupled carriages that are articulated to turn with respect to each other on the plane of curvature of the guide, and in which at least a power source is positioned in a carriage of its own.
 59. The apparatus of claim 57 wherein the power source comprises a battery.
 60. The apparatus of claim 52, wherein a belt is passed around at least one drive wheel, said belt forming a loop that is arranged in a friction contact with the guide.
 61. The apparatus of claim 52 wherein the traction device comprises a drive motor which is an electrical motor.
 62. The apparatus of claim 52 wherein the speed of rotation of the drive wheel of the traction device is adjustable.
 63. The apparatus of claim 62 wherein the speed of rotation of the drive wheel of the traction device is adjustable in a stepless manner.
 64. The apparatus of claim 62, wherein the speed of rotation of the drive wheel of the traction device is adjustable by remote control.
 65. The apparatus of claim 52 wherein the traction device comprises a power measurement sensor in a fastening point of the tail of the web or the auxiliary member.
 66. The apparatus of claim 52 wherein the guide comprises a channel for a cooling medium.
 67. An apparatus for tail threading of a paper web in a finishing machine for paper, in which the paper web is arranged to travel along a predetermined path, the apparatus comprising: a guide which extends in a machine direction, and which has a friction contact plane, the guide extending along a curved path which curves in both directions in a direction perpendicular to its plane in accordance with the windings of the path; a traction device comprised of a plurality of carriages, which are arranged to move along and in relation to the guide, wherein a first one of said plurality of carriages comprises a drive wheel connected to a power transmission of the traction device, the drive wheel being arranged to transfer the traction device in relation to the guide by means of a power transmitting contact between the guide and the drive wheel, wherein the drive wheel is arranged in a friction contact with the friction contact plane of the guide, wherein the friction contact plane of the guide curves in directions perpendicular thereto in accordance with the travel path of the paper web; and wherein a tail of the paper web or an auxiliary member for threading the tail of the paper web is connected to one of said plurality of carriages. 